I was under my car last night and I noticed something new. Last year I ran a 50/50 mix of supreme and av gas. My headers were always black with soot inside. This year I'm running straight AV 100 which I'm told is leaded and my headers are spotless inside. They look like they were washed out with brake cleaner they are so clean. Is this normal? My 1050 has 96/96 jets in it since the dyno and the plugs looked ok to me when I pulled a couple at the track.

Yes, I rebuilt the engine last winter and made several changes from last year. Basically I only reused the rods, crank and block - everything else has be changed. Went from. 10.90's in crappy air to 10.30's in the same air.

When the exhaust is black most of the time it means you are running rich and when the exhaust burn a light tan color mean the air to fuel ratio is pretty close on spot. But if it never changes color you are to lean and your plugs should show a lean burn look, my Dad always used the plugs and the color of the exhaust to tune all his before everything changed to fuel injected. I learn this when him and my brother raced a 69 Mach 1 Mustang and I use this way when messing with a carb engine.

Last edited by 69F100 on September 11th 2014, 12:51 pm; edited 1 time in total

Your collectors need to at least be light grey to tan . Out here in California , I run my daily driver fairly lean on 87 ( pure white porcelin on the plugs) yet the tail pipes are still pitch black. This happened after the lead was taken out and other CRAP was put into the gas so we can breath easier.

Down here in Florida 100 AV gas is called 100LL and its a low lead fuel, maybe you could try adding a lead additive or a octane booster and see what happens, but the burn looks pretty good now but it may be a little lean in the cooler months, JMO,

butterbean wrote:Down here in Florida 100 AV gas is called 100LL and its a low lead fuel, maybe you could try adding a lead additive or a octane booster and see what happens, but the burn looks pretty good now but it may be a little lean in the cooler months, JMO,

It's only a "low lead" fuel when compared to the Avgas of old. The old aircraft fuels had a ton of lead in 'em. Current "low lead" Avgas has roughly the same amount of tetraethyl lead as our old leaded pump gas.

Its other (often overlooked) benefit is that it stores very well and doesn't go bad quickly like the crap at the corner gas station. An awful lot of aircraft sit for months at a time in all kinds of weather with minimal ill effects to the fuel. Try that with your favorite auto gas.